Pro's: If your child or a party uneducated about the safety bullet tries to use this weapon, they would not know how to correct the malfunction.

Con's: Using this bullet as a piece of mind to leave your weapon unsecured. Possibility of activating the bullet at a critical moment. Rodding a weapon with a loaded magazine poses safety issues (unless you safely remove the magazine).

I think the idea is unique and has uses, but I would never RELY on it to ensure my children do not tamper with my firearm. I would use one however, depending on the price.